In my prior U.S. Pat. Nos. 3,971,123 of 1976 and 4,113,166 of 1978, both of which, in so far as they are relevant, are incorporated herein by reference, I have disclosed processes for the continuous casting of metal, particularly steel and steel alloys, more economically and yielding a superior product than the conventional processes of casting the molten into ingots, or sections of large cross section.
Briefly, it is well known that when molten metal is cast in an ingot mold or continuously cast in an open-ended water cooled mold of an ingot or billet size that the grain structure and composition of the outside of the casting is superior to that which forms the core within said outside layer. This is due to the fact that the thin layer of metal first formed on the outside of the cast body solidifies very rapidly because of its contact with the inside surface of the mold, but inwardly from this outer shell, often referred to as the chill-zone, the metal solidifies at an increasingly slower rate. The slower cooling results in an increasingly coarser grain structure and a migration of alloying constituents toward the center of the section. To correct this condition, the steel, before or in the process of being converted into finished products, must be hot worked and heat treated in various ways.
In my two patents above referred to, the metal is cast into thin strands of chill zone thickness which are of fine grain structure and of substantially uniform composition throughout, having been rapidly cooled and solidified. After solidification, but preferably at a temperature where the metal is sufficiently hot that it may be pressure welded, or upon subsequent reheating to a pressure welding temperature, a multiplicity of these strands, or sections thereof, may be layered, each layer after the first being pressure welded to the preceeding one to produce a thick body for conversion by rolling, forging or other process into a finished product. Since this body of layered and integrated sections has a uniform grain structure throughout and has any alloying constituents uniformly incorporated throughout, the heat treating and hot working required of conventionally cast ingots or billets are reduced or eliminated, as are such equipment as ingot molds, blooming mills, etc.
In my two patents above identified, various casting procedures and subsequent consolidation of multiple layers are disclosed. In the earlier of said patents thin strands of metal of uniform chill zone thickness are produced on the periphery of rotating chilled rollers that dip into a body of molten metal and which I term "dip-rolls". The thin layer of metal which solidifies on the periphery of each roll is stripped as it is formed and adequately solidified and these thin strands are then consolidated under pressure while they are hot enough and in a state to be progressively pressure welded into a single integrated strand. In the other of said patents a metal belt moves continuously in contact with a pool of molten metal retained againt the surface of the belt and the cast strips so produced are layered in various ways and pressure welded to produce thick sections of metal of uniform quality.